1. Field of the Invention
The present invention relates to remote-controlled unmanned robotic vehicles. More specifically, the present invention relates to remote-controlled vehicles capable of movement within the air gap between a rotor and stator of a dynamoelectric machine to tighten wedges in the machine's stator slots.
2. Description of Related Art
In dynamoelectric machines and, particularly in the stators of large dynamoelectric machines, it is conventional to build up an annular magnetic mass by stacking thin laminations of magnetic material on key bars. The laminations conventionally include slot-shaped openings therein which are aligned in the stacking process with corresponding openings in all other laminations to form a set of parallel slots in the inner surface of the annular magnetic mass. One or more conductors are placed in each slot to receive the generated electricity if the dynamoelectric machine is a generator or, to receive the driving electric power if the dynamoelectric machine is a motor. The conductors in the slots of a large dynamoelectric machine carry large currents and are subjected to large magnetic fields. They therefore experience very high forces tending to displace them within the slots. If steps are not taken to prevent such an occurrence, the forces acting on the conductors are sufficient to displace them in the slots and to damage or destroy the stator.
In the power generation industry, hundreds of stator wedges are often used to assist in retaining the coils in the stator of a power generator or a motor. The wedges are positioned to overlie the coils. The stator wedges are positioned into wedge grooves or wedge slots formed in the peripheries of the core laminations within the coil slots. The laminations are conventionally formed of coated steel material. The stator wedges are conventionally formed of an epoxy-laminated glass material. Because the stator coil laminations are formed of a coated steel material, it is important that such wedges be formed of a non-conducting material so that a short is not created which can damage various portions of the generator. During use, the large magnetic forces generated by the rotor of a large dynamoelectric machine are sufficient to distort the cross section of the stator from circular to slightly elliptical. The major axis of the elliptical distortion rotates with the magnetic pulse of the rotor at a speed of, for example, 3,600 rpm. The stator slots are thereby cyclically widened and narrowed a very small amount at a frequency of 120 Hz as the maxima and minima of the elliptical distortion travels there past twice per revolution of the rotor. With years of normal operation of such dynamoelectric machines, the stator wedges holding the stator coils can become loose. An undetected loose wedge condition can result in excessive vibration of the coils and eventually lead to a catastrophic failure of the machine. The typical assembly for a stator slot includes the stator coils, stator wedges, and wedge filer material. Normally, when wedges become loose, the generator rotor has to be removed, the loose wedges are removed and new wedges and filler material are installed. This is a time-consuming and expensive process.
Stator wedges have been developed that can be tightened after they have been installed. This style wedge has a main body that is tapered on the underside to which a wedge insert (tapered to match the wedge) is slid beneath it. As the wedge insert is forced against the wedge in the taper of the wedge, it increases the thickness of the wedge assembly, thus compressing the slot contents and tightening the wedge in the wedge grooves or wedge slots referred to above, which are also referred to as the dovetail.
It is an object of this invention to provide an apparatus that can tighten such wedges without removing the rotor.
It is a farther object of this invention to provide an apparatus that can tighten the stator wedges remotely.
It is a further object of this invention to provide such apparatus that can tighten the stator wedges from within the air gap of a dynamoelectric machine remotely under the supervision of an operator.